The invention relates to a valve device intended for use in an apparatus for examining human metabolism processes through analysis of the breathing air, said valve device being provided with a connection for a patient mouth-piece and a connection for the connecting hose to the apparatus, and also having an inhalation valve which is placed in such a way that it opens through underpressure or negative pressure as a result of inhalation and admits ambient air, and an exhalation valve which is placed in such a way for the apparatus connection that it opens through excess or positive pressure as a result of exhalation and allows the exhalation air through to the apparatus.
Valve devices of this type in which the housing was in the form of a T-shaped pipe section were used hitherto. The connection for the patient mouthpiece was formed by the body of the T, while the crossbar of the T contained the inhalation valve at one side and the exhalation valve at the other, and the apparatus connection was, of course, also fitted at that end.
This existing valve device had two major disadvantages. In the first place, the total weight was quite high, so that it had to be supported. Secondly, it formed a considerable dead space, which meant that the results of the analysis were affected, or compensation had to be made for them.